There are applications in signal processing, and other areas, which could use dispersive surface acoustic wave (SAW) filters with very long time delays. The maximum delay of conventional dispersive delay lines is limited to about 30 microseconds using a standard size (4 inch) mask on standard size substrates (3 inch). Delays above 30 microseconds with SAW dispersive are possible, but the substrates become very expensive and construction of the device is very difficult. The present invention overcomes these limitations with a dispersive structure which uses a surface wave confined to a narrow, single-mode waveguide.